From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5B40C1CF8CE; Sun, 24 Mar 2024 22:47:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711320446; cv=none; b=jYx1vBHiKNVcY4xDkrJVRsb5iIy2c5rpghys4DE4ILbAGo7WAN9k+zhgzQSvKyTzYv/wUazPlWqRIdTW3Wk7hc+8TjhyJgFhgg2mmg+0VRSdo96weZhbur28VLbpHhzYrMd8pgk7YWeGdXMA84B3WaV/4cva05GKV6tRzlPu+6Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711320446; c=relaxed/simple; bh=7s3O442lwN7lnTlv6pQRkhF/q7B5OZA+IrXKh4D9bj0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=KaKzd7SJ7jd11vJcKGfVB015JdJVeMyBl2VCCnuoMtQcfshoCUz6GL0BUFprQkMWSXeR/aRjibVnls+JBJwLE2z8CQpe6oVO3ek08h/B7A1iFbspLwmCRRzPBp2OfYLmlN4cQ0dZksud8qnJD2MTZS37E3qNHqff3sb+xAoDXvU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IiWF1uoX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="IiWF1uoX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7953FC433C7; Sun, 24 Mar 2024 22:47:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711320446; bh=7s3O442lwN7lnTlv6pQRkhF/q7B5OZA+IrXKh4D9bj0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IiWF1uoX2jpml3cI9Pb1xVp/qAUhZ8AuTMa9tKw8BYUAX6lobbvCoaBPAzVstOyFW ykZZ4XGvmSJwUzWaG7NhHE1eJbZRKeU8w/1/Txk/TAgFPQ5T/14vxidCmTEIZbDJha RtcUyaBlQcJ+CCNDGyvYBc+LWSkCPl9BkVEWcjqK1X5uvErvhHE3kIpeEgNAGFipPA GuS7EU+qryxuQzp73bEtnDy0P7YRn2GmY93nHvLc1vQ1pIUxVQ7AkKfkjr3OVT3NTW R+Y/Oew6w3ZY5QaxTA/CnJLzw/kZtp5aEMi1KzwJvb9+sEiFQw1id031zAKh4QQ2RB akiGMghJMdl/A== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Johan Hovold , Bjorn Andersson , Dmitry Baryshkov , Sasha Levin Subject: [PATCH 6.7 004/713] soc: qcom: pmic_glink_altmode: fix drm bridge use-after-free Date: Sun, 24 Mar 2024 18:35:30 -0400 Message-ID: <20240324224720.1345309-5-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324224720.1345309-1-sashal@kernel.org> References: <20240324224720.1345309-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit From: Johan Hovold commit b979f2d50a099f3402418d7ff5f26c3952fb08bb upstream. A recent DRM series purporting to simplify support for "transparent bridges" and handling of probe deferrals ironically exposed a use-after-free issue on pmic_glink_altmode probe deferral. This has manifested itself as the display subsystem occasionally failing to initialise and NULL-pointer dereferences during boot of machines like the Lenovo ThinkPad X13s. Specifically, the dp-hpd bridge is currently registered before all resources have been acquired which means that it can also be deregistered on probe deferrals. In the meantime there is a race window where the new aux bridge driver (or PHY driver previously) may have looked up the dp-hpd bridge and stored a (non-reference-counted) pointer to the bridge which is about to be deallocated. When the display controller is later initialised, this triggers a use-after-free when attaching the bridges: dp -> aux -> dp-hpd (freed) which may, for example, result in the freed bridge failing to attach: [drm:drm_bridge_attach [drm]] *ERROR* failed to attach bridge /soc@0/phy@88eb000 to encoder TMDS-31: -16 or a NULL-pointer dereference: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 ... Call trace: drm_bridge_attach+0x70/0x1a8 [drm] drm_aux_bridge_attach+0x24/0x38 [aux_bridge] drm_bridge_attach+0x80/0x1a8 [drm] dp_bridge_init+0xa8/0x15c [msm] msm_dp_modeset_init+0x28/0xc4 [msm] The DRM bridge implementation is clearly fragile and implicitly built on the assumption that bridges may never go away. In this case, the fix is to move the bridge registration in the pmic_glink_altmode driver to after all resources have been looked up. Incidentally, with the new dp-hpd bridge implementation, which registers child devices, this is also a requirement due to a long-standing issue in driver core that can otherwise lead to a probe deferral loop (see commit fbc35b45f9f6 ("Add documentation on meaning of -EPROBE_DEFER")). [DB: slightly fixed commit message by adding the word 'commit'] Fixes: 080b4e24852b ("soc: qcom: pmic_glink: Introduce altmode support") Fixes: 2bcca96abfbf ("soc: qcom: pmic-glink: switch to DRM_AUX_HPD_BRIDGE") Cc: # 6.3 Cc: Bjorn Andersson Cc: Dmitry Baryshkov Signed-off-by: Johan Hovold Reviewed-by: Bjorn Andersson Reviewed-by: Dmitry Baryshkov Signed-off-by: Dmitry Baryshkov Link: https://patchwork.freedesktop.org/patch/msgid/20240217150228.5788-4-johan+linaro@kernel.org [ johan: backport to 6.7 which does not have DRM aux bridge ] Signed-off-by: Johan Hovold Signed-off-by: Sasha Levin --- drivers/soc/qcom/pmic_glink_altmode.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/drivers/soc/qcom/pmic_glink_altmode.c b/drivers/soc/qcom/pmic_glink_altmode.c index 7ee52cf2570fa..ca58bfa41846c 100644 --- a/drivers/soc/qcom/pmic_glink_altmode.c +++ b/drivers/soc/qcom/pmic_glink_altmode.c @@ -469,12 +469,6 @@ static int pmic_glink_altmode_probe(struct auxiliary_device *adev, alt_port->bridge.ops = DRM_BRIDGE_OP_HPD; alt_port->bridge.type = DRM_MODE_CONNECTOR_DisplayPort; - ret = devm_drm_bridge_add(dev, &alt_port->bridge); - if (ret) { - fwnode_handle_put(fwnode); - return ret; - } - alt_port->dp_alt.svid = USB_TYPEC_DP_SID; alt_port->dp_alt.mode = USB_TYPEC_DP_MODE; alt_port->dp_alt.active = 1; @@ -525,6 +519,16 @@ static int pmic_glink_altmode_probe(struct auxiliary_device *adev, } } + for (port = 0; port < ARRAY_SIZE(altmode->ports); port++) { + alt_port = &altmode->ports[port]; + if (!alt_port->altmode) + continue; + + ret = devm_drm_bridge_add(dev, &alt_port->bridge); + if (ret) + return ret; + } + altmode->client = devm_pmic_glink_register_client(dev, altmode->owner_id, pmic_glink_altmode_callback, -- 2.43.0